Density Converter
Convert between kg/m³, g/cm³, lb/ft³ and lb/gallon.
lb/ft³
62.427818
from 1 g/cm³
kg/m³
1,000
g/cm³
1
g/mL
1
lb/US gallon
8.345434
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How the Density Converter works
The GKCalculators Density Converter instantly transforms density values between the most widely used units—kg/m³, g/cm³, lb/ft³, and lb/gallon—making it an essential tool for engineers, chemists, students, and anyone working across metric and imperial measurement systems.
Density is defined as mass per unit volume, and the challenge when working across scientific, industrial, and everyday contexts is that different fields favor different unit systems. Scientists and most international standards use the SI unit kg/m³, while chemists and laboratory professionals almost universally work in g/cm³ (also written as g/mL for liquids). Engineers in the United States frequently encounter lb/ft³ in structural and HVAC calculations, and the petroleum and food industries often specify density in lb/gallon. This converter handles all four units bidirectionally, so you can enter a value in any unit and immediately see its equivalent in the other three.
The conversion factors between these units are fixed physical constants derived from the definitions of the kilogram, metre, pound, foot, and gallon. For example, 1 g/cm³ equals exactly 1000 kg/m³ because there are 1,000,000 cm³ in one m³ but only 1000 grams in one kilogram—the ratio simplifies to a factor of 1000. The relationship between metric and US customary units introduces irrational-looking constants: 1 kg/m³ equals approximately 0.062428 lb/ft³, derived from the pound-to-kilogram ratio (0.453592) and the cubic-foot-to-cubic-metre ratio (0.0283168). It is important to note that the US liquid gallon (3.78541 L) is used here rather than the Imperial gallon (4.54609 L) common in the UK and Canada—if you are working with British petroleum or brewing standards, be sure to confirm which gallon your source data references.
A common source of error when converting density is confusing the unit of the gallon in use. US lb/gallon and Imperial lb/gallon differ by about 20%, which can cause significant errors in formulations, shipping calculations, or material safety data sheet interpretations. Another frequent mistake is conflating density with specific gravity: specific gravity is a dimensionless ratio of a substance's density to that of pure water at 4 °C (1000 kg/m³ or 1 g/cm³), so a specific gravity of 0.85 corresponds directly to 850 kg/m³ or 0.85 g/cm³—but it is not a density unit itself and cannot be entered here directly without that mental conversion.
To get the most accurate results, always verify the temperature at which a density value was measured, because density is temperature-dependent for virtually all materials—especially liquids and gases. Water, for instance, is 999.84 kg/m³ at 0 °C but only 958.4 kg/m³ at 100 °C. Standard reference temperatures are 4 °C for water-based references, 15 °C (59 °F) in petroleum standards, and 20 °C in many chemical databases. If your source and destination applications assume different temperatures, a unit conversion alone will not be sufficient and you will need to apply a temperature-correction factor before or after using this tool.
Formula
1 g/cm³ = 1000 kg/m³ 1 kg/m³ = 0.062428 lb/ft³ 1 kg/m³ = 0.0083454 lb/US gallon 1 lb/ft³ = 16.01846 kg/m³ 1 lb/US gallon = 119.826 kg/m³ General form: ρ_target = ρ_source × conversion_factor
Pro tips
- Always confirm whether lb/gallon values in your source documents reference the US gallon (3.785 L) or the Imperial gallon (4.546 L)—the difference is roughly 20% and is a frequent source of costly errors in formulation and logistics.
- When working with gases, remember that density is highly sensitive to both temperature and pressure; convert units first and then apply an ideal gas correction (using PV=nRT) if conditions differ from the standard state of your reference data.
- For quick sanity-checking, remember that water is exactly 1 g/cm³, 1000 kg/m³, 62.43 lb/ft³, and 8.34 lb/US gallon—any material denser than water will exceed these benchmarks, and any less dense material will fall below them.
- If you are working with specific gravity values from a material data sheet, you can treat the specific gravity number as equivalent to g/cm³ and enter it directly into the converter to obtain kg/m³, lb/ft³, and lb/gallon equivalents instantly.
- When comparing densities across multiple materials for engineering decisions (e.g., selecting insulation or buoyancy calculations), convert everything to kg/m³ first—it is the most universally accepted unit and avoids compounding conversion errors across steps.
Key terms
- Density
- — The mass of a substance per unit volume, commonly expressed in kg/m³, g/cm³, lb/ft³, or lb/gallon depending on the field of application.
- kg/m³ (kilogram per cubic metre)
- — The SI standard unit of density, used in most scientific literature, engineering standards, and international specifications.
- g/cm³ (gram per cubic centimetre)
- — A metric density unit equal to 1000 kg/m³, widely used in chemistry and laboratory science; numerically equal to specific gravity for water-based comparisons.
- lb/ft³ (pound per cubic foot)
- — A US customary density unit common in construction, HVAC, and materials engineering, approximately equal to 16.018 kg/m³.
- lb/gallon (pound per US gallon)
- — A density unit used in the US petroleum, paint, and food industries, where one US gallon equals 3.78541 litres; distinct from the Imperial gallon used in the UK.
- Specific Gravity
- — A dimensionless ratio of a material's density to that of pure water at 4 °C (1 g/cm³), numerically identical to density in g/cm³ for direct comparison but not itself a unit of density.
